Traditional display devices typically include an array of light valves disposed between a light source and an observer. For example, in liquid crystal display devices, such as those used in laptop computers, the light valves are formed from liquid crystal material disposed between a substrate and a glass cover. Individual light valves defining pixels of an image are created by forming a common electrode on the substrate and patterning a matrix of pixel electrodes on the glass cover. The liquid crystal material reacts in response to electric fields established between the common electrode and pixel electrodes to control the electro-optical response of each of the light valves.
For monochrome displays, the light source provides a uniform distribution of light, which is selectively passed by the individual light valves to produce the monochrome image. Multi-color displays are achieved by interposing a color filter array between the light source and the array of light valves, such that the light entering each light valve is preselected in wavelength. For example, a common color filter array used in display devices is a checkerboard pattern of red, green and blue filters.
However, the range of color reproducible by a display incorporating a color filter array is limited by the spectral content of light that passes through the filters. For example, most wavelength selective filters have substantial transition bands that necessarily reduce the range of spectral content of the transmitted light. As a result, there is a reduction in color fidelity in images produced using a color filter array. In addition, traditional light sources (e.g., CCFL light sources) that are typically used in color displays are known to be deficient in wavelengths corresponding to a red hue. Thus, irrespective of the quality of the filter for red light, the spectral fidelity of the image may be impaired in the red hues.
What is needed is an illumination device capable of producing a predetermined spatial pattern of light at different wavelengths without the use of a color filter. In addition, what is needed is an illumination device that enables the use of light sources with a wider color gamut than traditional light sources.